First off, I honestly feel that these specialists upgrades are easily the best expansion packs that have been released. They offer a lot of versatility, and options for the game. For anyone just picking up the game, from this point, I would say these are a ‘must buy’.
The adding of generic non named commanders helps with immersion in my opinion. You can easily get a 3d printed analog to add yourself into the game, or write your own little character bio if desired, by no means is this a necessity, but for many it will be fun.
The expansions add in more universal command cards, further diversifying the choices when building an army, as well as personnel upgrades to make your units perform an extra role, which opens up tactical options for a game. All of these are great things.
Now, as the title says, this thread is for theory and conjecture with the underlying idea that another specialist pack will be developed, and here is where we can theorize what it should contain.
My first hope is that the second specialists pack contains another generic officer commander. I would personally be fine with a reprint of the generic commander card (and personnel upgrade), but an alternate sculpt.
I have no doubt that more generic command cards would be included as well.
Now comes the fun! What further personnel upgrades could be included? We have repair droids, medic droids, comms technicians - these are all great, but, what we dont have are some generic heavies. This is where the specialist 2 pack could find its niche. For the empire a T-21 repeating blaster would be a great option. The blaster was seen being used by sandtroopers in A New Hope, so it makes it a viable option. Having a choice between A DLT trooper and a T-21 would be great. I imagine the t-21 would be similar to the rebel z-6
Rebels could get an analog for the DLT, and with no better option, in my opinion, than using A gigoron (The white shaggy alien, named Moroff, from Rogue One). A long range heavy for rebel corps would be great.
Now, the above examples, I wouldn't want to see a straight copy of each opposing corps units weapons, but a unique take on the weapons. The imperial t-21 might roll three black.
Now if we go by the current specialist packs, we still have a couple minis to work out. What I think might be useful, and seen in many video games, is a unit (likely another heavy) that puts down a portable shield generator this could provide heavy cover but require a unit to be immobile, and/or a recover action to ready. You sacrifice attack power for a defense upgrade. Good for imperials, as well as rebels.
This would leave one mini left to decide. While the previous examples have been heavy units, I don't think that should be a requirement. A personnel upgrade that offers a training upgrade could offer some unique options, though that may step on the special forces/operative toes a bit too much.
Another option, is another heavy, but one that can fire grenades at a longer range, perhaps requiring a grenade upgrade to be purchased.
I think one of the imortant things is, for the rebel specialists, they include some more non humans. Droids are great, but with the multitudes of aliens on the rebels, this would be a great place to include different sculpts.