How TNA's game will do all depends on the developer, IMO. I personally hope they get EA BIG to do it. The same guys who do the Def Jam series. They based their system off of the No Mercy system, and tweaked it a bit for Def Jam 2 to make it more of a fighting game. So if they just stepped back a bit and made a wrestling game like before, it would probably be pretty good.
As for SVR2006 - I'm getting hyped. The last one I got hyped for was HCTP and it honestly didn't disappoint me. I will still probably rent this one first, though. The only downside to that is that my local Rogers usually only gets 2 max copies of whatever wrestling game in, so it's never available for the first few weeks.