I would wait until after E3 and weigh that decision.
those are 3 different things that could happen and there's no way of me knowing all the details that would matter to me or you.
I'm betting on 3DS, but if I were to choose another system, I would be eyeing PS3 closer than the 360 mostly because I think Kinect is gonna gonna flop hard and MS is gonna want to fix it's black eye with a new system before it leaves a permanent mark. With a PS3, atleast you get free online a powerful HTPC and a Bluray player whether you buy into Move or not (which I believe is a better wiimote in most ways except for when pointing at the screen).
The PS3 will always be useful regardless of PSN/XBL support and for that kind of money, I'm gonna want it to serve a secondary function long past it's games support. and since I think that Nintendo is gonna keep their 5 year cycle tradition intact(Wii2 in 2011), I'm sure that Sony & MS are gonna try and follow suit before 2012 is over (MS may even try to rush a launch in 2011 if Kinect belly flops as hard as most of us are expecting) depending on where Wii2 specs fall.