So the only question is: is the turn on which you expect to trash the hovel in the natural course of buying green cards late enough that you'd be willing to take a free estate?
This is absolutely the wrong question because it begs the question about Estate buying fitting into the normal rules of deck building. Pre-Dark Ages, you don't want to buy Estates too early because then your deck chokes on green cards; you have lots of shuffles of dead cards with very little benefit.
Hovel changes this dynamic. With Hovel in hand, buying an Estate does not increase the number of dead cards in your deck.
The right question is instead:
does the benefit of buying an Estate on turn X outweigh the cost of buying an Estate on turn X?The answer to that question is: if X is late in the game, when we want any green card we can afford, then the benefit of buying an Estate obviously outweighs the cost. This is roughly the same calculation pre- and post-Dark Ages. (I say roughly because the math changes slightly since Hovel can be trashed, but I haven't run simulations to see if the difference is large enough to warrant a change in the Big Money buy rules.)
But, if X is earlier in the game, we need to examine the issue more closely. The pros of buying an Estate are: getting an extra VP. Small bonus, but a bonus. The cons of buying an Estate
used to be having an extra dead card in hand, but now we're trashing Hovel, which was also a dead card, so that con no longer applies. This was the main reason we didn't want to buy an Estate in 2p when there were still 5 Provinces left, but now we're not having the effect of clogging our deck more.
The other con of buying an Estate is that buying an Estate costs a Buy. On turn 2, that might matter if the board has a useful $2 card. But if it doesn't, then that con doesn't outweigh the benefit of buying the Estate.