Too late for that. The Astute programme is already well under way. The first two have already been launched and construction on a further two is already well under way. Worst case scenario will see the Trafalgar class being kept in service a little bit longer.
If you are talking about replacements for the bomber subs, its already been established that they will be replaced come hell or high water (even the lib dems have acceded to this)...
No, not the Astute program (although they may shave number 6 and/or 7 off). I’m talking about the NEXT generation after that (initial work already being done).
As for the boomers, they may “program slip” them (retain Vanguard for longer) or they may replace them with cheaper alternatives. It depends if the commitment is to nuclear armed submarines or an independent deterrent. They could replace them with bombers or (my preferred solution) cruise missile subs.