MSD bought Mallory recently and as a result, the Mallory VW distributor is now out of production.
So I bought a MSD 8545 distributor to see if it's a viable alternative.
The first difference is that the MSD distributor can't trigger a coil and requires one of their spark boxes (6AL for example).
The next thing we found is that, since its designed for a Type 1 engine, the supplied clamping bracket is unusable. The stock T4 clamping bracket can be used with a suitable spacer to hold the distributor at the right height.
The cap uses HEI type wires, so I'll need to change our custom wire sets for the new application. (MSD makes wires for the T1 that are unlikely to fit a 2L T4.)
The advance mechanism is actually easier to set than with the Mallory.
Overall, the construction appears better than the Mallory, but the added cost of the spark box makes it more expensive overall. At least the added cost can be (more-or-less) justified by the built in rev limiter.

Does this mean that the Mallory Unilite caps and rotors are also going out of production? If so, I better stock up while I can.

They still make Unilite distributors, just not the one we used.

How about the modules ? Will they still be available ?

I think you should upgrade to the MSD setup just in case they dry up.