Provided atomic swaps between XMR and BTC eventuate, BTC will be forcibly implanted with an XMR privacy light switch, hard linking the two.
One would assume the regulatory lid, generally sinking on privacy, that negatively affects the XMR price – e.g. illegal to trade in South Korea and Japan, delisted on certain exchanges globally etc. would start to turn against BTC. Likewise turning against any other future crypto atomic-swap linked through to XMR or lesser privacy coins.
It's extremely likely privacy crypto will see increasingly negative regulation over the years. At the least, the risk of negative regulatory attention is far more likely than vice versa. Every governmental security and tax body obviously wants visibility over XMR. See those IRS contracts to crack XMR recently. When unsuccessful these bodies will invariably pressure for more regulation. End result, the inability to turn XMR into fiat through an increasingly banned BTC would lead to increasingly worthless crypto. Some contrarian tax haven nation might still allow trade into fiat, but anything transacted there will always be scrutinized heavily internationally.
Without the ability to change to fiat in your kyc bank account, in a country you actually want to live in, privacy linked crypto becomes basically worthless unless it's accepted as payment natively for all the mundane to luxury stuff you want. Not going to happen in any significant way if the laws of the land have moved to prohibit it.
So assuming society goes down the increasingly cashless route over the years, and therefore privacy-coinless route, I'm wondering if XMR receives its heyday for a time after atomic swaps. Then as the years/decades roll by, and the gears of regulation slowly grind against privacy crypto, anything in the crypto family that can be linked, like BTC, is regulated till it's worthless in most places.