Any pugilist welcomes the opportunity of a ringside seat where a potential future antagonist is on the bill. Russia and the USA greatly enjoyed China's discomfiture in its ill-judged 1979 assault on Vietnam. Three years later, the Russians took a close professional interest in our recapture of the Falklands, from which they learned several lessons. Even more salutary for them was Gulf War 1 in 1991: they'd been skeptical as to whether the NATO AirLand Battle doctrine was workable, and discovered to their dismay that it was. (This helpfully persuaded them to sit out the 1990s, when a less chastened Russia might have lashed out as a diversionary tactic against its post-Communist humiliation.)
Yes - better to discover what your future opponent has got in his locker by watching someone else lead with their chin. It is therefore confidently to be anticipated that the Chinese will be watching Iran vs election-year-USA with considerable interest and close attention.
The Iranians pose a serious challenge - irrespective of any baby nukes they may possess, which they wouldn't squander anyway. Amply capable of 'conventional' fighting, they must also be the most potent initiator of asymmetric warfare on the planet right now (of which the cyber variety is just one facet**). For one thing, the Chinese will want to see how the Iranian drone fleet fares. Don't be surprised if it is swept from the field ... but to achieve that, the US will need to show its technological hand.
Likewise, even the slightest escalation of violence will tempt Trump to take out the Iranian nuclear programme - but again, using what technology? (FatBoy wants to know the answer to that one, too.) More broadly, what means will the NSA deploy to intercept small-but-deadly operations against US assets the world over? Or to blot out Iranian comms across the spectrum?
Finally, and on a different theme: high-profile conflict in one theatre has often been used as useful cover for some other party to have a crack at something they've had on their own list for a while. I still don't think China will go for HK (see Predictions 2020 quiz, qn 5), still less Taiwan this year - even on a wet Thursday morning when all eyes are on a spectacular going down in the Gulf: but Someone will try Something.
Have a nice weekend! Oh - and I wouldn't be taking a holiday in Cyprus any time soon ...
** cyber is a game lots of folks might start playing, in the hope it all gets blamed on Iran