USAF is seriously looking into purchasing/converting F-15 2040C variant. It will be a direct competitor to Su-35S, still a paper plane but technologies are ready, and if they enter service they'll have a better avionics package than Su-35S (few years more 'modern' technology).
This is interesting because Americans do not see this as a direct-to-combat competition as it was back in the Cold War. 100-150 Su-35S is still peanuts comparing to numbers USAF fields. F-35 isn't competitive in markets outside usual American clientele, while Russians (Sukhoi) have been scoring $ in neutral markets. Countries like Malaysia, Indonesia, Morroco, etc... are not tied to a particular block and are keeping mixed origin military. Russia wasn't competitive right until the end of last decade because they didn't field the same types they were advertising as uber. Only when VVS/VKS (RuAF) started fielding their own advanced types, and especially after using them in warfare over foreign soil, orders started rolling in.
These days, Russia sells to anyone that wants to buy, with certain exceptions here and there. Americans have a priority list, which doesn't just denote how fast somebody gets an article (place in queue of production lines), it also means the customization/strip-down depth and price cost. Russians have something called export article, and types will be denoted by either E (eksport) or K (komercijalni), like MiG-31E or Su-27SKM. Export article is same for everyone. That's not how U.S. rolls, they will sell great F-15s to Japan for a comparatively fair price, but they will sell bullshit, stripped down, price inflated F-15s to Saudi. Which is good for humanity but U.S. is not about altruism, it's about state interests and they don't want tech to leak from KSA.
In any case, if you aren't part of U.S. circle, you aren't getting any sort of F-35, while the market outside the circle is fairly large. U.S. has found itself in the situation where they market paper planes like F-15SE (Silent Eagle) against real planes like modern Flankers or Rafales/EF2000, at loss. This potential introduction of so called 4++ generation F-15 variant, based on proven technologies and building on the framework of one of the best fighter jets ever concieved, could do much both at home and abroad. Even if you disregard my opinion about F-35's capacities (and I'm no aerospace engineer), it's convoluted development process, moving of deadlines, increasing cost, decreasing numbers, problems with each trial iteration, etc., should be enough to figure out that USAF wants an interim solution.
The exactly what Russians did while waiting for PAK FA initial operational capacity.
P.S. it's funny how F-22 was caught idle in the military history. There simply isn't anyone realistically interesting to use F-22 against. Still the best fighter jet fielded ever, basically idling under high maintenance costs. USAF wanted 700 F-22 as a crucial air superiority measure against projected 1500+ Soviet Flanker and Foxhound variants (with about a third being 'modern' upgrade package in late 80s timeframe). Well Soviets sure AMRAAM-teased the poor Raptor, just said nope and took a walk