Curious to the comments about hopefully keeping him for 3 or 4 years.
Not to say surprise firings can't happen, but the only legit step up from us who may have an opening soon is Arsenal, and I highly doubt they'd go with Lambert, although Lambert is very Arsene like in his transfer policy.
If we keep progressing at a good, natural level, I don't see any reason why he shouldn't be here for the next decade.