It is a tough question.
I have been trying to build up an IT business full time in the past 5 years, and I think if I can attract a big business to buy me out, I may need another 5 years (it may never happen).
Yidian is only one year old and big guy like SINA is interested. Yidian is at the right time doing the right thing. Yidian learns from the other overseas Chinese literature forums. Make it better if not most famouse one. Also yidan's system - discuz, is better than most other forums, and may make it easier to merge to sina. Yidian's mission concentrate on overseas Chinese literature, keep it clean and simple also may play a role here.
In other words, yidian is at the right time doing right thing and yidain is new, clean and simple, make it a candidate for buy out. If you let this opportunity go, you may never see it again.
1) the owners will get some money or maybe some big stocks
(I hope that sina will be generous).
2) yidian will expand and yidian will attact more writers and readers.
3) yidian will have sina's big budget for the future growth.
1) it will be a business, and busienss will be for money.
2) it will not be a quiet tea house anymore, it will be a starbucks. Not the yidian owners or friends originally wanted it to be.
3) if it is sina china, it will follow the Chinese government's governing rules.
If not sold now
Advantage is yidian will still have the freedom to do everything the owners and yidian friends want.
1) How long can the owners and donators can keep yidian running, in terms of money and time?
2) Yidian will grow but it will grow very slowly. If it grows too slow, when more and more other similiar forums appear, yidian may fade out slowly later on. If that is the case, then sold out can get money now, and keep yidian alive for a longer time (may be not the exact same yidian).