Telegram already has "more than 100,000,000 monthly active users" with "350,000 new users" signing up each day and it delivers "15 billion messages daily" according to a post from February found in https://telegram.org/blog/100-million.
Also, Telegram clients are open source:
https://core.telegram.org/#getting-started
Some work is being done, as we can see here:
http://trac.miranda-ng.org/log/trunk/protocols/Telegram
But I still wonder why is it taking so long to have a working protocol for Telegram, thus the ticket.