If you're talking about software exploits, the obvious CFW devs and hackers have reverse engineered probably every last byte of the relevant code that would actually be able to provide useful access for a hack to take over the system. Just because nothing has been found doesn't mean nobody bothered looking.
the 360 had its disc drive flashed after less than a year, so it isn't like it didn't have a hack until Jtag. Jtag just opened the doors wider. a better comparison would be the PS3, especially considering how for all of its commercial life you needed a PS3 below a specific revision to hack it just like the switch, while almost every version of the 360 was hackable in someway.
Honestly, they might. We are led to believe the only difference with the OLED Switch is the new screen. Which means the SoC and everything else is the same. Also it might be out of Nintendo's hands to fix, it might depend on Nvidia releasing a fix as before.
Nintendo only ever seem to put as much effort into patching exploits and generally making life hard for pirates as they think they can make back the monetary investment on through sales to people that would otherwise be pirating. The SX chips don't seem to be manufactured anymore, there might not be much financial incentive to go any deeper to block them, so Nintendo might consider it problem solved.