I work at one of the Tier 1 firms. To be honest, transferring later is do-able but not done that often (unless you do an MBA in-between). One reason for this is that bankers learn a certain way of thinking and doing things which can be hard to 'un-learn' coming across (e.g., there is a large difference between IB models and consulting models - they are for different purposes). Another reason quite frankly is that once people start working in IB, they start earning a bunch of money (more than even tier 1 strat), once people start earning a bunch of money they (in general) start to feel like they need this amount of money (and even more!) just to survive (it's a tragedy that I've seen overtake some of my friends and felt myself). Therefore, IB-ers become unwilling to take a pay cut to work in strategy (even though the money is more than ample and they may find the job more enjoyable).Overall my advice would be if you want to do a job (be that Strategy, IB, candle-stick making, whatever) and you have a chance to do it now then you should just do it. Trying to second-guess the future and say "if I do this for two years, then I can do that for one, then I can finally get this" doesn't really work in practice, things get in the way. If you know what you want and can do it now, then do it.