Simply put, no new arena in San Diego and no current prospects for one anytime soon. The Chargers have been having trouble getting a new stadium built, and the Padres' Petco Park faced lawsuits before it eventually opened. That said, I don't think a new arena will be built down there until the Chargers' stadium gets settled first, or if some investor or corporation steps up and builds a new arena on their own dime. My wife and I took a trip down to San Diego last month, and our hotel was across the street from the Valley View Casino Center (formerly the San Diego Sports Arena). The neighborhood where the arena is located is surrounded by a few hotels, several shopping centers, and many restaurants...it's situated just east of Sea World, and located near two major highways (Interstates 5 and 8). Although it's kinda in the heart of the city, the neighborhood is very "suburban" like. Probably the best location for a new San Diego arena would be downtown, perhaps near Petco Park.
Meanwhile, Anaheim has tried for years to lure a team to Honda Center (including the Clippers), but of course to no success. In fact, Donald Sterling was ready to move to Anaheim by 1997 until he got a change of heart, and decided to stay in Los Angeles. Also, there's an old L.A. Times article available online (from around '97) where the city was ready to build a new arena for the Clippers in the Sports Arena/Coliseum parking lot (18,000 seats, 80 luxury suites, plus new team offices, and practice facility), but plans for Staples Center came out at the same time, and we all know what happened after that. Of course, not too long ago, the Sacramento Kings were planning on moving to Anaheim before those plans were abandoned. Since Anaheim/Orange County is part of the Lakers and Clippers territory, the Kings would have not only paid a relocation fee to the NBA, but also a territorial fee to both the Clippers and Lakers.