NO FUCKING WAY this will not hurt Vegas. Right now Vegas is making more money in their clubs than their casino floors. I play poker all the time in casinos through out the midwest and at EVERY SINGLE TABLE there's always someone talking about "I just got back from Vegas" or "I'm going to Vegas next month." They can literally play poker in their back yard but they still go to Vegas.
When you go to Vegas you can only bet on the current games (and a few futures) anyway. Think about it, you think some fuck in Erie PA is gonna say "damn I can sports bet at Presque Isle Downs & Casino, now I'll never have to go to Vegas again!" I don't think so.
Also, bookies are also still going to do fine since they won't be giving up 10, 12 or 20 percent to the state or the sports leagues as well.
This doesn't affect people who are already betting, this affects guys who currently don't know anyone to bet with, and may get a few new fans interested in the leagues now that they can legally wager. Look at what sites like Draftkings did for Nascar and MLB. Since when did most people south of the Mason Dixon line give a fuck about Nascar? "Oh I can bet on the races now? sign me up!"