So there are two question in this thread : the first one being the OP's question "I' m a KSP1 early adopter will I get KSP2 for free?" and the second one being "Should KSP1 early adopter's get KSP2 for free?"
I will attempt to answer each in turn:
So as answer to the first question, I should say no, as no statements have been issued to this effect and that Star Theory is a different entity to Squad.
As for the second the answer is longer:
Firstly we must define what the transaction in place for KSP1 is, as the OP seems to want to replicate this system for KSP2 : even if at first glance the transaction resembles this : Squad ---> Early Adopters it cannot be that way however since the labor put into making the product the early adopters received must be payed for, so the transaction should be this : Other Buyers <---> Squad ---> Early Adopters, or : Squad Employees <----> Squad ----> Early Adopters, (obviously these examples are simplified and treat Squad as an isolated entity, which it is not but the principles are there) so when an early adopter gets a DLC for free they are either making the price of the DLC increase or making the salary of Squad employees decrease or else making Squads profits decrease, which results in less work being able to be payed for, so less growth and new content for every one.
So then we must answer two more questions: 1.Why should the Early Adopters receive a product for free? and 2.Why should they not?
1. In general, one receives monetary/material compensation when one either works or buys, with this model the Early Adopters act like share-holders in a public company, they receive money/products because they invested/brought shares/the game. One could say they receive material compensation because their early investment allowed us all to have fun with this game and that if they had not bought the game it wouldn't have existed, however in this sense the game we play would be radically different without modders, but should we give them DLC's for free ?
2.Even if the arguments above are completely valid we have shown that the "Early Adopter Policy" adopted by Squad acts as a weight which results in lower salaries for employees and less content at a higher price for the other users, and such an decrease of happiness for every one, despite what Bertrand Russel says, I should not and am not happy to throw my money away...
So we can at last answer the question we asked ourselves in the first place: "Should KSP1 early adopter's get KSP2 for free?" to which I answer :
No, they should not, for the reasons that I have said above as well as reasons cited by @The Aziz , Star Theory should not make the same errors as Squad and will, I hope , not make them for the wellfare of all : from the community, to their employees... Plus the fact that there was no mention of a sequel in Squads promise which is the base of the "Early Adopter Policy".