If u liked Wii Sports tennis 2 players, u should try it 4 players  ;)

As for WM+, Sega would have had development kits for it for about 10 months, i think that would be enough time.  It's too bad Sega Superstar Tennis or Mario Tennis: Play on Wii didn't have WM+ though, i would rather play those than virtua tennis  :(

YEA, I played Wii Sports Tennis with other three friends, I couldn't beleive how great it was.

I am not sure about 3rd party interest towards WM+, it is a peripheral that now is not in the market and at the moment there are 0 users with WM+. Of course, I think it will have huge sales when WiiSports Resort is released.

Well, look @ Balance Board support. Quite a few games use that, i'm sure many more games will use M+. Also, EA is coming out with a M+ tennis game so they will have to compete.

Well, that's my 2 cents anyways.