From a Scotland perspective (which was one of the constituent parts of the UK who voted to remain*, alongside Northern Ireland), I would hypothesise that Abellio may exercise their break out clause when due in the event of a no deal Brexit. Bearing in mind it has been reported in other threads that Abellio/Nederlandse Spoorwagen are or were having cashflow problems recently, and are/were being investigated in the Netherlands for fraudulent practices over the award of a franchise there.
Should if there be a second independence referendum, I can see the result being more clear cut this time, but cannot predict which way. I do not know how this would affect the sourcing of parts and various railway equipment, or if trains will be built in Scotland again.
PS I have tried my best not to be too political here.
* As a side note, there is a democratic deficit as Scotland and Northern Ireland voted remain, with concerns regarding Brexit not appearing to be listened to at Westminster. Since the 1979 General Election, Scotland have voted as follows:
1979: Mainly Labour, got Conservatives
1983: Mainly Labour, got Conservatives
1987: Mainly Labour, got Conservatives
1992: Mainly Labour, got Conservatives (only just due to a late swing during the day)
1997: Mainly Labour, got New Labour (which were not new, and were most certainly not Labour)
2001: Mainly Labour, got New Labour (which were not new, and were most certainly not Labour)
2005: Mainly Labour, got New Labour (which were not new, and were most certainly not Labour)
2010: Mainly Labour, got Conservative - Lib Dem coalition
2015: Mainly SNP with 56 out of 59 constituencies, got Conservatives
2017: Mainly SNP, got minority Conservatives with support from DUP
All of the above shows that Scotland does not get the government it has voted for. I do understand the support for Scottish independence, but I do not support the SNP's version of independence.