Somebody mentioned this on Twitter, but it's something I've been thinking for a while.
The Bears really can get away with just an assignment sound safety next to Jackson for as long as he's playing at an elite level. The last 3 years, they've gone with Amos, Clinton-Dix, and now Gipson at the other safety spot. Amos was already around, but they made no effort to re-sign him. HHCD was allowed to walk. And I expect Gipson will be walking also since he's over 30. All of them were pretty good, but the first 2 haven't really been missed.
The play of Houston-Carson, and previously of Deon Bush in nickel and dime situations makes me believe/hope they keep the same philosophy for SS in the coming years. Keep re-signing these two to 1-2 year deals if they are open to it. I wouldn't even hate going into the season with them as the 2nd and 3rd safeties instead of 3rd and 4th. They are both assignment sound, so they won't kill you if they have to start. And they won't prevent you from signing a guy that's sitting out there on waivers next summer. Both are only 27, so you can conceivably do this for a few more years before you absolutely have to find someone long-term.