It's really up to you. Once softmodding and USB loading is solid on vWii, then that will make it that much more attractive. When softmodding and USB loading is possible on the Wii U itself, then it'll be a no-brainer.
As of right now, you can purchase and download Wii U games directly to either system storage or external USB storage, eliminating the need for the disc. Although I don't know the specific details about how this works. It was said that retailers will also sell the digital versions of the games (retailers will have control over the price), so you can't just go to the Nintendo Shop and download NSMB, BO2, and ZombiU directly without out first buying the digital version from Wally World or wherever.
The bottom line is, if you want one and think you'll use it, then by all means pick one up. If the Wii U titles don't entice you as it stands, then there's not much harm in waiting. There may be hardware improvements in the future which will help the system run faster, however, just as with the Wii, there may be hardware "improvements" which make softmodding harder. BootMii as Boot2 vs IOS comes to mind.