1. The F-35 is not designed for dog-fights. It is designed as a stealth attack platform. No planes are going to get within 30 miles of it without being engaged.
2. Just WHO is going to take on the IAF? Syria with crusty old MIGs? Iran with F4s? Iraq has like 3 F-16s? Turkey? Saudi Arabia? Russia and Israeli are now friends thanks to our inept foreign policy.
Russia has supplied Syria with air superiority, fighter bombers, and ground support jets. The MiG-31s the SUs are equivalent or perhaps superior to anything the US possesses and have supplied Israel with - including Israeli upgrades. Nothing the Israelis can do to its existing AF will make fundamental changes in performance characteristics; they can only alter various load-outs and software - neither of which will change any stealth characteristics, speed, turning, weight, or thrust among many others.
Syria among others, as time goes by, could and will challenge the IAF: Iran is buying large numbers of advances planes from both Russia and China. Others are buying fourth gen planes from Europe. Read the article.
Russia and Israel have a temporary military working agreement, not a friendship. Russia intends to install multiple S300 systems in Syria, effectively shutting down all secret cross-boarder ops by the IAF - even in Israel.
No planes get within 30 miles of a F-35? Perhaps, but only if the F-35s have F-22s covering them. Most Russian BVR missile ranges are in the 100s of kilometers.
The F-35 “stealth” is not anywhere as good as one might think. And is largely a useless boondoggle. Its BVR missiles have to be strapped on externally as they do not fit internally, thus eliminating what little stealth the F-35 committee-designed plane possesses.