Can't see that being an issue as the UK / Britain has never existed as far as FIFA is concerned. Makes more sense than a stand-alone England bid after finishing last for 2018. I'm sure having the options of including some of Hampden, Celtic Park, Ibrox, Murrayfield, Millennium as options would boost chances.
I think joint bids will become the norm going forward as these major sporting events are so incredibly expensive to host.