Time machine, people, time machine. No way to know. Relative salaries fluctuate based on reimbursements, technology, and laws among other things.
I know internal med docs who start with $250K offers as hospitalists with 80 hr./week schedules and $140K offers with 40 plus 20 call, so it just depends on how much you want to work. I'm just using general IM as an example because people think that it is low-paying. It doesn't have to be.
Plenty of threads/websites are available on this topic. None of them can predict the future. Every specialty has a reason to be lucrative in the future. They all have reasons why physician compensation is dropping too.
Wanna make money? Be a provider that charges cash only before services rendered. Set your prices, and let your customers go back to their private insurance for whatever reimbursement THEY will get (not you). Plenty of all-stars out there do this and make over a million a year. The trick is you can only serve patients with the dough to afford you, and you have to be good enough to merit the asking price. But you'll get paid that way if you have the customer base to support you.
http://www.newyorker.com/fact/content/articles/050404fa_fact