I seriously doubt BMW won't bring the triple turbo diesel to the 3 series...
The x drive system is coming to the uk for F30, the 3 series is the most important car for BMW and the whole point of M Performance is to compete with Audi(nary)'s S models of which the S3 and S4 are probably the biggest sellers.
Plus the fact M550d isn't coming to uk adds further to this.
Lastly the only 5 series to outpace 3 series are the M division models (with the exception of 335d which hasn't been upped to match F10, yet), so if the F30 can cope with the engine size/power I see no reason for there not to be an M350d... It'd sell like hot cakes.
There could even be room for an M350i too.
But beyond all of this BMW need to make a new M1 and if it has to make a profit just make it very expensive and limited edition, something that devours the R8 and is hot on the tail of the McLaren