The Phillies looked at a couple of locations, Broad & Spring Garden and later 12th & Vine. In both cases, the proposal died in the face of a combination of ferocious resistance and lack of public support. Vince Fumo, who at that point was still at the peak of his power, essentially declared holy war against it and vowed to defeat it by any means possible (either through his then-proxies on City Council or in the courts). He and higher-income people in Fairmount didn't want it close to them while Chinatown's leaders eyed the 12th & Vine location for their community's expansion and development and were more than willing to head to courts as well and played the discrimination card when they did.
The opposition does not appear to be the same for this since it will be replacing a failed shopping mall and won't be encroaching on Chinatown's or anyone else's turf. The leader of the Chinatown Development Corp spoke out in favor of it.
I like the idea, to be honest. However, as was said when the city talked about a Center City ballpark for the Phillies, it will take a sea change in the habits of Philadelphia sports fans. Philadelphia is a car town and people like driving places and, hence, they like the sports complex which was built to be driven to/from. I can't help but wonder if that is an overreaction to the sad last few years of Shibe Park/Connie Mack Stadium when fans had to park on neighborhood strees and be extorted by neighborhood husslers offering to "guard your car" (or else...). Like MSG in NYC, this arena will literraly be upstairs from the train station and be a block away from PATCO. Fans in South Jersey will pay to park at a PATCO station and pay a PATCO fare in lieu of using more gas, paying a bridge toll and then paying to park at the complex. Folks in the Pennsylvania suburbs will pay to park at a Septa station and pay for a train ticket for a regional rail train to the arena. I imagine that in most cases, the cost will come out in the wash. Instead of tailgating before the Sixers game, people can head to one of the many local eateries or watering holes.
But yes, there are a host of what ifs. WIll Comcast fight back? Will the Flyers try to move in? Where will Villanova play its big arena games? You can almost certainly bet that if Philadelphia hosts another major political convention, the Sixers arena just a couple of blocks from the Convention Center will be the site of the prime time show.
Another good thing....the Sixers won't have to go on the annual Mickey Mouse road trip every Holiday week (unless Disney decides to take over that area).
As for the question of what will Philadelphia do with two arenas, things seemed to go fine when the WFC and the old Spectrum were still there. The old Spectrum was torn down only to make way for the underwhelming XFinity Live facility.
Believe it or not, this is CBP's 19th season and LFF's 20th. Are we getting close to the 2/3 point of their useful lifespans? Down in Nashville, the Titans are replacing a stadium that just opened in 1999 and Turner Field only lasted twenty years as the Braves' home.