must be Joking !!!! ... Kindly don't post anything like this without a legit Source....
and How could you say this Confidently ???
Are you trying to being sarcastic ???
are you a Insider From Microsoft ??
I'm not Microsoft insider, but I say this based on a few observations.
Firstly, there's the fact that Microsoft says only "modern" Lumias will receive the Windows 10 ugprade. Why didn't they simply say WP8/8.1 devices will get it? That's because the phones that came out in 2012 like Lumia 920/820/520 etc are not considered "modern".
Secondly, Microsoft originally said when releasing Lumia x2x devices that they'll receive 18 months of support. The 18 months period included WP 8.1 -- hence those updates were provided. But Windows 10 will come out 36 months after those phones were released. It's clearly outside the supported timespan.
Thirdly, their latest blog clearly says not all WP8 Lumias will be upgradable.
Fourthly, the only phonse missing in the January 21st conference are the older x2x Lumias. Other than these all other phones were seen running Windows 10.
Put these things together, and it's easy to conclude why the x2x series won't receive the upgrade. Even through the Developer Preview they won't be upgradable.