zonoma,
That is a tricky one. On flights wholly within CAS, we are cleared to the destination and will go there if the radio fails, pretty much following the flight planned route and altitudes, and the only times we hold is when we have been given estimated further clearance / expected approach times or arrive earlier than at flight planned time.
But also, the rules say that when losing RT while outside controlled airspace, we should not enter it; which will apply as soon as I leave it temporarily on my planned route.
In real life, I would decide what is safe, in VMC divert to somewhere sensible, and in solid widespread IMC I would continue my flight planned route. I would also default to re-entering CAS as planned - at least then I am doing something expected, rather than turning up on the ILS of some en-route diversion unannounced and unexpected, or at the destination half an hour later because I had to fly around CAS rather than through it...
But I just made that up - what do the controllers here think?
In real life, at that point also the good old ICOM comes out of the flight bag and I would use that to talk to ATC and sort something out, and maybe the mobile might receive something as well...