I do hope technology has evolved a little bit since 1966.
As for planning, unless my ETOPS alternates are below minima or there is a cyclone sitting on my flight track, the flight will depart. Any enroute WX affecting the flight will be briefed before departure and dealt with enroute. I think this is a pretty universal practice.
There seems to be some sort of consensus that this accident was in part caused by WX. AF 447 would not have left RIO without a working WX radar, given the enroute forecast. So if the WX was a factor (I'm not saying it was), why would they even go near it?
I have never flown through a CB in my entire career. I've been pretty close, in between, touched the edge, above, but never IN one. I've been 100 miles off track to avoid the monsters, in areas where only HF was available. There are contingency procedures for this scenario.
A failed Wx radar enroute would give the pilots some challenges. Continue, divert, return? They could have gone through WX already, so a turn back may have not be a good option. WX enroute to alternates could also be bad. So they would have found themselves between a rock and a hard place, trying to pick their way through CB's visually.
I don't have any statistics, but WX radars seem to have more failures than other systems. I had one fail on me just yesterday.
Pure speculations on my part, I really, really hope they find the cause of this one.
BTW, would a WX radar failure be an Acars event transmitted to maintenance?