-Snip-
The progression for refuelling is 20k, 30k, 40k, 60k, 90k, 135k, 200k, etc.
The small craft version still exists, with half the previous refuelling rate.
I do believe then that the main benefit you obtain from having more, smaller tankers is when your fleet is overall very low on fuel. What I mean by that is if you have one large tanker, and ten ships to refuel, then it can only refuel one ship at a time, and so depending on the fuel level of the fleet, you might run out of fuel on the other ships before you finish refueling the fleet, ( I do believe it refuels ship by ship, not the fleet as a whole). Having more numerous smaller tankers however allows you to not only double your refueling rate at the very minimum due to each needing a refueling system, but instead of only refueling one ship at a time, you can now refuel two, three etc, reducing the odds of your fleet running out of fuel while on the move as your tankers will move through your fleets twice as fast.
This generally isn't an issue if you have a tanker that can keep up and it's refueling capacity exceeds the total fuel burn of the fleet, but you can see where in certain cases this might lead to several interrupts for out of fuel. So I would like to request that you consider if another module or Tech can be added/researched that allows for increased simultaneous refueling. Whether this splits the total capacity or in a sense multiplies it is up to you, but it would be a workaround to smaller tankers being superior as you mentioned earlier. If one large Tanker can refuel say 4 ships at once(A good maximum, four ships flying in a plus formation around a tanker seems doable), it is doing the job of 4 smaller tankers. Though making the refueling systems heavier and more "powerful" as you've done would also shift the balance more in favour of larger tankers in general.
As for possible release dates to this long awaited update, are we looking at something late July/August if all goes well?