I would hope that Triumph would extend warranty to any bike that was bought before this lockdown began. I doubt it though. With the winter / floods / COVID -19, mine has become an ornament.
Provided that you have your bike serviced on time and by the dealer then Triumph could well look favourably should you have a problem in the third year.
I bought my thruxton r last November and parked it up for the winter, so the first 4.5 months it never turned a wheel. I did manage to get a couple of hundred miles on in late March before the lock down. I had a verbal agreement with my dealer about getting the first (500 mile) service once this years season had started, which was good. Like @andypandy says I reckon it is unlikely that Triumph will extend the warranty, if it was my company I don't think I would....
I can only speak from my own experience, it was a few years ago but I had a new swinging arm fitted by the dealer as a warranty claim, FOC several months after the warranty expired
