Of course Trump and the GOP can try all sorts of voter suppression, which is what they're doing now.
Meanwhile, delaying or canceling elections through executive order would be blatantly illegal, particularly when no conflict is taking place on U.S. soil. The case likely wouldn't even make it to the Supreme Court, but if it did, I have no doubt elections would be promptly reinstated.
I'm not saying the Supreme Court has a perfect record, of course. Not even two years ago, they essentially ruled that the president is above the law. But at least in matters regarding the balance of powers between branches, the Supreme Court is wary of the power of the executive branch, and that should certainly include the president's ability (or lack thereof) to interfere in elections.
Claiming this strike on Iran is an attempt to suspend US elections is exactly as ridiculous as claiming the last round of strikes on Iran, or the Maduro raid, or any of Trump's other previous military boondoggles were attempts to suspend US elections.