Scotland has fifty-nine of the 650 MPs but there is enough room only for about two-thirds of the whole lot so there will be no physical seats being taken away.
If Scotlands does decide to leave, then I would expect the remaining boundaries in England, Wales, and NI to be redrawn. But I don't think they will leave, unless things change rapidly in the next few weeks.
The should be fewer members, unless they shrink existing constituencies and create more of them, but I can't see them pulling out the seating. Just means more room to get their head down for a bit when the debate becomes boring.
If all of Scotlands MPs disappear from the UK parliament, so does the Labour party's potential majority. For all time. That means Tories in government for ever.