With Picard in command of the Borg, or at least giving advice, I guess anything is possible...
But the E-D was faster than the Cube, and able to catch up with it once before already. Dialogue establishes the Borg had already left; subsequent VFX doesn't show the Borg dropping out of warp to kowtow with the E-D (even though the Chrissie transcripts suggest this) but simply being at impulse (that is, sans starstreaks) when Riker hails them, but it's clear the E-D caught up with them. They didn't stay back and wait, they got caught.
What took them so long? Well, we don't know how long it really took. "Emissary" would have us believe the battle was over in a jiffy, with very little time elapsing beyond what was seen onscreen there. After the battle, Riker deals out new jobs for his officers, then goes to brood in his Ready Room, where Guinan talks with him, and during that short talk he is told that they are arriving at Wolf 359. The interval between "deals out jobs" and "talks with Guinan" could be all of twenty-five seconds, meaning the Borg really left posthaste after winning the fight. Or it could be five hours, meaning the Borg had time to build new ships, discover religion, abandon it as inefficient, retune their eyepieces, and then proceed towards Earth.
Timo Saloniemi