If restaurant wait personnel get $15/hr will tipping be prohibited?

No one can stop you from tipping. Restaurants in California have tried changing things, both to distribute money to the back of house staff and to make up for the wage hike they have had to give to servers. There are several variations, including building in the service charge, and saying that no tip was necessary. But the point of a tip was always to encourage good service. I've been in countries where tips are not common, and believe me, you don't want service from people who are not motivated to be nice to you!  I will always tip for good service. 

I know many restaurant wait personnel who make FAR MORE than the $15 min wage already, so it would have little or no impact on them.  There is certainly no valid economic reason to prohibit tipping.  Income is income and it's all taxable by the IRS.

Yes, trying to live on tips is stupid, knowing that tipping also completely optional, so there's that. 

Some states have tinkered with prohibiting tips and gotten themselves sued by various unions and some employers ended up forking over millions of dollars in misappropriated "fees" paid in lieu of 'tips".

Nope. But restaurant staff won't have to rely on tips to get adequate pay.