^^^ This. While I'm not an astrophysicist and I could be wildly oversimplifying the concept here, I understand the "big crunch" implosion to be the result of the internal force of the combined gravity of all matter within the universe overpowering the force of the initial blast of the big bang. Since it does appear to be a "simple" matter of gravity overtaking explosive force, then the Q could easily stop the implosion. However, as Third Nacelle
said in the earlier post, it is not a foregone conclusion that they would be inclined to do so. They just might want to shift over into another, possibly newer, universe in greater need of custodianship/torment.
Then there is the other theory, growing in popularity among cosmologists called the "big freeze", where the universe will continue to expand, as it has expanded (via momentum from the big bang) beyond the threshold for internal gravity to pull it back. If this were to happen, time would eventually slow down, all the stars would burn out through a lack of general molecular excitation and the universe would become a truly cold and dead place. The Q would then almost have to increase the gravitational constant of the universe in order to preserve general molecular cohesion and allow new stars and new life to continue to be reborn. Again, if they cared to do so.
If they really wanted to save the universe, they would have to subtly adjust gravity over time to a point where the universe comes to rest at equilibrium, between explosive and gravitic forces, so that it maintains its size for eternity.