The Big East doesn't necessarily alter ABC or ESPN programming very much when it comes to Saturdays. Virtually all of the ABC slots the conference has taken up have been regional, usually paired with a Big Ten or Big 12 game. The conference fill around 4-6 Saturdays slots during the year on ESPN or ESPN2 and those could be replaced by games from other conferences. They also filled around seven Saturday ESPNU slots per year and those could end up being extra ACC, Big 12, Big Ten or SEC games.
The weeknight slots will be somewhat tougher to fill. The ACC and Pac-12 will allow for a limited number of Friday games as will BYU, but the Big 12, Big Ten & SEC typically do not. It is possible that more games from the MAC & Sun Belt will show up on Fridays instead of mid-week. If ESPN successfully bids on a subset of MWC games, possibly the Boise St. home games or another package, they could also fill Fridays.
Basketball is the bigger hole to fill when you look at is as losing games from the 10 team Big East plus the Catholic 7. Some of those slots will come back to ESPN as they pick up additional ACC games with the addition of Syracuse and Pittsburgh to the conference. As Louisville enters the ACC and Rutgers & Maryland shift to the Big Ten, the networks could get a few more slots, but that doesn't seem like its enough to fill all the time available. Its possible that they'll take additional ACC games from inventory, maybe from Raycom's ACC package along with their own regional SEC package before they announce the 24/7 SEC Network, but its a huge hole. Around 5-7 games.
RSNs like SNY and MASN would lose some key programming supplied from ESPN Regional TV, but don't be surprised if SNY maintains a Big East presence, particularly with its connection to NBC Sports Regional Networks. A network like MSG may be out in terms of taking on a portion of the regional package from SNY but could end up aligning itself with the Catholic 7 as could MASN.
But there's a catch...
Always is. It is possible that ESPN could match the offer NBC presented the conference and keep this content. There would still be a hole in men's basketball, but a much smaller hole and one that can be easily filled. The AP article also noted that NBC would have the ability to sell games to other networks, which could mean that ESPN could buy some Big East content for their networks. Same with the Catholic schools if FOX elects they want a variety of programming. Trading games with ESPN? Maybe. Who knows.