Essex have just lost a 4th wicket, so that game is still alive.
If Essex win, any hope of a home QF disappears. As does any chance of knocking them out of the top four. But it would keep Middlesex two points below us with one game left, and increase the distance between our NRR and their NRR (which is still close enough to easily be overturned by one round of matches).
If Middlesex win, they move back level with us, but probably still behind us on NRR (because if they are to win this game, it would surely be a very close win where their NRR for the game is close to zero). And it keeps Essex within touching distance of us (including if their final game was to washed out).
If it's a tie, that's actually a great result. It would keep Middlesex below us on points (as well as hampering their NRR). They would have to beat Surrey to have any chance of overtaking us - which could be useful, denying Surrey two points - but ultimately it would remain entirely in our own hands (which it wouldn't if they beat Essex). And at the same time it would keep Essex from pulling too far clear of us (our NRR is better than theirs, were we to beat Somerset and they to lose to Gloucs).