On the one hand your post mentioned a very general "making good on the LEP" but now you seem to be only specifically referring to some discrete "premium content" that was announced by Zac long after the LEP sales had been discontinued.Read the OP maybe? There was an intention to supply something by the end of 2018 that didn't happen.
I can understand anyone being naturally disappointed with regards to having to wait for those elements of premium content, but I hope you realize no one paid a single dollar for that particular promise made by Zac in 2017. What you paid for was a LEP sold sometime in the period 2012-2015 that very explicitly didnt include a specific timeline at all for any of its elements (including Zac´s).
As mentioned I can understand you may feel dissappointed and it is up to FDEV to decide how to treat that, including refunding you if they so deem apporpriate, but in order to "make good on the LEP" as per the conditions and description when you purchased it they do not really need to. Especially if the new era recently announced is actually delivered.