Mixed feelings. On one hand I think too much time has gone by for this, Flying Circus is so fondly remembered but there are serious rose tinted glasses in play. I watched some full episodes recently and there was an awful lot of filler/pieces that just aren't much good. If you watch the classics for which they are remembered as a highlight reel there is real genius, but coming back together after so long I'm not sure it could be replicated in a one-off show.
On the other hand... It's Monty Python and I think I'd probably be unable to resist trying to get tickets for it and watching just on the off chance that its something brilliant.