I don't see it being cancelled, but I do wonder if BBC1 are no longer building it in as a tentpole of the schedule, which could end up with them dropping seasons altogether in favour of four or five specials to run at bank holidays as convenient.
That's possible and it may make sense in the short term, but I'm not sure how viable it would be over the long term from a production standpoint. The Writer's Tale
indicates that RTD and Gardner had difficulty getting money for the Specials Year, partly because foreign broadcasters weren't interested in it.
While they have confirmed that there will be a Series 8 next year, I have just realised that they haven't said how many episodes it will be. (I'm not going back to check them all but they did confirm 14 episodes for Series 7.)
If the coproduction or outsourcing rumors are true, it's possible that the BBC itself doesn't know yet because they're still negotiating the deal and don't know what their production partners are in for and want.
If the BBC America coproduction rumors are true, I'd expect a run in the Copper
or Ripper Street
model -- eight to ten episodes broadcast in a single block.