Andrew Marr to leave the BBC

[XIII]

That would be my guess, and probably as part of a "revitalised" / reformatted Sunday morning show looking to skew younger than Andrew Marr's version. I wouldn't be too surprised to see a schedule change to support that aim. And, if this came to pass, I would be even less surprised to see the traditional BBC Sunday morning political programme re-invented a few years thereafter.

Laura is a similar age to when Andrew Marr took over from David Frost which is why I think she's probably the most likely candidate.