You need to think long term. Isometric DND based RPGs are making a bit of a comeback with kickstarter, which is fantastic, but underneath publishers they are still dead. Purchasing the Enhanced editions is an investment in Baldur's Gate 3. It's a way of showing interest at the very least.
That's personally the only reason I see to really buy them, as the added content doesn't entirely justify the price in my mind. And it still can't compare to BGT.
Not really, the series doesn't need another sequel. After you kill all the other demi-gods what more is left to do? Watch that incredibly annoying half-elf druid shoot out kids? No thanks.
The only reason to buy the "Enhanced" versions is to play them on an iPad or if they get off their butts an Android tablet.