Wow, I really love philosophical questions like these. Reminds me of the times when I took philosophy classes and discussed with my colleagues about it.
Hmm, that would create a very weird phenomenon. The entire concept of time travel is a bit flawed since those not "time traveling" will experience time as if nothing had changed or happened. Consequently, you going forward in time to get the iPhone 5 would have no effect whatsoever in changing "history" or the flow of events, since this is already built in.
Either way, time travel requires many assumptions: one of the big ones is that this space and time we are in right now is "stored" in some universal file vault. How else could you "return" to a time in the past? Furthermore, for you to go "forward" in time right now, there needs to be a space/time in the future. That in itself requires a huge assumption: that there is a future ahead. If such is the case, then it would mean that the future ahead is fated, since any actions anyone does now are pre-determined (somehow). There goes the argument for free-will vs fate.
So... hypothetically, if we accept all these assumptions and you did go forward in time and then came back to "present" time, then I suppose yes, Apple could sue you. But it wouldn't really matter in the overall scheme since you didn't change anything by time travelling... it already existed and remains unchanged.
Anyway, thanks for reminding me of my days back in philosophy classes.