OP are you me because I am debating between the 2012 13'' Air and Pro for nearly the same exact reasons.
I used to own the 2011 13'' Pro for my last year of college. However, I ended up selling it afterwards because the resell value was still high and I no longer needed to carry a machine around classes (I have powerful Windows machine at home). Anyway, I loved the fact that I could upgrade the SSD and memory on my own for reasonable prices, which I did.
I am probably a more niche example, but being in software development and working constantly with various IDEs and editors, the smaller resolution was less than ideal for me. While working on projects, I found myself wishing I was on my desktop, which didn't even provide that much more real-estate (1440x900). I'm not saying the 1280x800 was absolutely terrible and unusable. For word processing, office tasks, and most if not all web browsing, the resolution was fine. Also, my friends who also had Pro's seemed to get along well on the Pro screen, so I had thought maybe it was just me who was used to working with more space.
I honestly wouldn't be too optimistic about gaming performance out of the 2012 13'' Pro. Yeah, CS:GO will probably run great on custom settings. In terms of Skyrim and SC2 though, I wouldn't expect ideal performance. Especially SC2, which is heavily cpu-bound. Ivy Bridge isn't a big step at all compute-wise from Sandy Bridge, and I could barely get acceptable frame rates in mid to late game scenarios with all low settings playing against the game AI. I haven't tried Skyrim, but who knows, maybe the HD4000 can handle it pretty well.
For me, the decision comes down to what I really need versus what I think I want. The new machine, whichever one I choose to get, is supposed to be my on-the-go workhorse; powerful enough to substitute as a primary non-gaming machine. I'm not going to be gaming when I'm out and I'd rather game on ideal settings on my desktop at home. Screen real-estate and portability (although the Pro isn't that heavy) out-trump the upgradabilty of the Pro for me. I'm not going to need more than 4GB of memory. Hell, my non-gaming memory usage never exceeds more than 3GB. I'm not the type that leaves like 20 youtube tabs open.
I'm almost certainly going to go with the 2012 Air. It just seems like the better machine to get at this current time. The 2012 13'' Pro probably still has its uses, but it's for a very specific niche: those who absolutely require the need to upgrade, can work with the lower resolution, and don't mind heavier/thicker form factor.