Pep showed Deco, Ronaldinho & Eto'O the door at Barcelona so I doubt very much that he will hesitate on Mahrez. Truth is, I believe he has failed to live up to expectations anyway and that there is a degree of buyer's remorse with him despite not being a poor acquisition. Riyad simply hasn't been the protagonist enough when given opportunities to be decisive.
Considering his absence in the run of biggest matches tells you quite a bit about how much trust Pep has in him. The right offer/suitor comes in, would be a good move for all involved to part ways IMO - even across town to United