I'd recommend not updating to 5.x in general. The advisory warning isn't there for shits and giggles. Yes, 5.x is vulnerable but in the sense that if you are dedicated enough you will have an entry and it likely will be released as an entry point to CFW pro-bono to fuck over TX's attempt to profiteer on piracy/CFW.
Your only entry is F-G, and its details are not yet divulged but it won't be a simple matter of a payload over the internet ala the software solution that we'll have access to with <4.x where we have easy TZ access due to nVidia's stupidity. It may also be unstable or finicky or not-for-the-faint-at-heart or do-at-your-own-risk ventures ala the good old days of phone modding when you fuck around with the bootloader by poking and proding the hardware.
With Mariko, as I said before, on the horizon and the shift of chipsets to T214, we're very VERY likely to lose hardware exploitation (almost assuredly F-G and the bootloader will be fixed up significantly) for some time if not in perpetuity and 5.x is already hardened against many/most/all of the flaws exploited on lower firmwares. That means new/left over exploits will become a precious commodity to potentially offer an in on Mariko. Wasting vulns that may carry over to Mariko is a long-term loss for very, very short term limited benefit.