Travelling after naturalisation but without the passport

With introduction of 6 weeks waiting time for the first time passport applicants - is it possible to travel with your foreign passport and ILR during this time? Technically ILR should not be valid after you have become a citizen?

With current speed of processing I have a strong suspicion that my wife's citizenship will be granted just before our planned holiday and I do not want to lose the holiday - leaving the country with the foreign passport is not a problem, but will she have troubles on her return?

See here.

I successfully travelled with my foreign passport and ILR after being naturalised without any problems.