Is there any reason to believe the R&A is looking for new venues? Hoylake was recently re-included (with mixed success, in my view); Carnoustie and Turnberry recently rejoined the rota after long absences. With St. Andrews every five years and Muirfield and Sandwich pretty solid, it seems pretty crowded already. I suppose you could substitute a course for Lytham or Troon and no one outside of those areas would be too upset.
If they were to go somewhere else, it would make sense to me to make a big splash, such as returning to Portrush or hosting the first Open in the Republic of Ireland at Portmarnock.