Your G2 is perfectly fine for learning photography. I think getting a DSLR is overkill in terms of the cash you will have to spend. I started out young with a conventional SLR but didn't really learn much till I got my G3 (even though that is ironically a "downgrade" other than for the digital bit). I quote what I wrote in another thread about cameras/photography in general:
My take...
I started with a Nikon (FM2? can't remember the model number) SLR when I was in primary 3 years ago and then moved on to a Canon F1 SLR in 1985/1986 by virtue of hand-me-downs by my dad who is an award-winning photographer. However, much of what I picked up about photography was from what I read in books rather than picking up the skills from my dad. Wasn't that much of a frequent photographer then because I wasn't that independently mobile, schoolwork prevented me from having photography as a regular hobby, and the costs of photography was too prohibitive as a young student back then.
At the encouragement of my dad, I took part in a couple of inter-school competitions... Got a couple of consolation prizes but hardly ever touched a camera on a regular basis unless I went on holiday.
Fast-forward to a couple of years ago... Ever since starting work and earning my own pay, the financial independence as well as mobility plus time for a serious hobby has allowed me to purchase first a Powershot S10 as my entry-level camera to digital photography. Even so, the S10 was reserved more for snapshots and holiday pictures on and off. Fast forward to more recent... about 8 months ago, I purchased my first prosumer: a Powershot G3. Whatever manual controls the camera had rekindled my interest in photography as a student. Being able to set my own exposure settings manually as opposed to the S10's "dummy" settings allowed me the creative latitiude to do the pictures that I want and like. The G3, though not an SLR, has controls that were close to one. The instant-preview nature of digital photography allowed me to learn at a pace that would not have been possible with a conventional camera (at least you did not have to wait for film to be processed and then analyze your results at a later date!). Couple with the usefulness of a live preview and a flip-out LCD, my dad was able to teach me a lot of the finer points of photography than what was possible with a conventional camera. My interest rose by leaps and bounds (see some of what I managed to achieve with my G3 at
http://engloy.elcreations.net), especially when I managed to get several of my pictures exhibited at a public exhibition recently, and when I got a highly commended award at the recent UOB Painting of the Year exhibition. And these pictures were all taken with just a humble prosumer G3.
However, within 10-11months of my G3 purchase, I am currently at crossroads. While I still enjoy the versatility of my G3, I find myself outgrowing the camera in terms of the exposure latitude/dynamic range that it can offer (despite trying to push the G3 further by using RAW captures), as well as wanting the freedom of interchangable lenses on my camera. And not to mention the cleaner shots/high ISO settings that I can achieve with a DSLR. The logical step for me is to move on to the 10D but I find the cost of the camera PLUS the lenses needed to achieve the same focal range of my G3 too prohibitive (easily up to $5k). The imminent launch of the very much cheaper 300D may be good news for me and I am waiting with bated breath for that camera which I am seriously considering buying.
The point which I am trying to make is that... yes... it's good to have a DSLR to start of with. I myself started with SLRs but which were luckily passed down to me without additional costs. Even though I had SLRs to play with then, it did not mean necessarily that I took great pictures then.
But if you are unsure about photography and where it would take you (whether if you would continue to take pictures, or simply drop it due to a lack of interest), my advice would be to go for cheaper option (but not necessarily "crippled", my Powershot G3 was pretty reasonable) rather than plonk all your money down on a DSLR plus lenses. Simply put, a cheaper camera does not equal to inferior photography and many would tell you, it's not the camera but the person that is behind the camera that really matters. Of course, a better camera will enable an already good photographer to capture even better pictures. However, the fundamentals of good photography still have to apply, and picking up these fundamentals does not entail having to have the very best in your equipment. To a certain extent, your equipment does determine how much interest you might have in photography. However, not having the highest-end equipment does not mean that you cannot continue to be interested in photography nor does it mean taking lousy pictures. As you progress, you might want to purchase better equipment naturally. You must however first progress or otherwise, photography would be just more of a matter of saying what high-end equipment you have rather than the quality of the pictures that you take.
Just my 2 cents worth