I'd argue that historicals learned successful marketing and sustainability from fantasy and SF, if the example of Flames of War is considered.
Admittedly, that's not a direct aspect of the genres, but of the approaches taken by a fantasy/SF leaning company (Games Workshop) being applied to WW2 15mm (Battlefront). Things such as emphasising the visual appeal over accuracy or believability, refreshing the game engine regularly with new editions and army guides, and pushing the game into a competitive, tournament format as a selling tool.
I do sometimes think thathad FoW existed when I first started gaming, I would have been drawn to the game by the visual appeal. As it was, 40K and other (but not all) fantasy and SF systems drew me in with better production values, and consistent ranges of miniatures. Historical rules back then were typed and photocopied, or, if they were flash, printed with a handful of black and white pictures.
Also, I recall being massively frustrated by the fact that the historical players at my local club would flit, butterfly-like, from one system or period to another. Trying to keep up with them left me with half-finished units for never completed armies, while I was always able to find opponents for my 40K armies, regardless of what was the 'in thing' in historicals.
Not really a 'lesson' that one genre can pass to another, but perhaps an indication of the problem of too many rules and scales across too many periods? Or are historical players just fickle victims of gaming fashion? ;)