I wouldn't say it's a "new" game as opposed to simply the next in the series. Sequels and expansions are pretty common.
If LH is successful we hope to make another game in the dowries in the future.
Not to be harsh, but imho, the jump from FE to LH wasn't significant enough to warrant $20. Maybe its because there wasn't enough brand new content added into it, it's just that nothing I experienced in LH couldn't have simply been done by the modding community had the scripts been open for modders to modify. There was very limited (if any) new assets, and most of the changes were philosophical rather than technical.
Not that I don't like the new direction, but I think with 20$, the game could've gone a lot further. With every RTS and TBS games out there, their expansion packs usually includes not only the overhauls to the formula, but also new content, toys, to play around with.
To elaborate my point, I believe mod Stormworld, is far more deserving of the 20$ price tag, than legendary heroes.
Maybe it's just me, but I believe refining the formula, fixes, and balances should be free, because these are the things that the developers failed to deliver.
Content should be paid, because these are extra things that are completely optional for the enjoyment of the game, but enhances it.