Kris Letang offered 8 years, 54 million.

Per Rob Rossi:

Letang was offered an eight-year contract at around $54 million (total), sources told the Tribune-Review. The Penguins' proposal contained little wiggle room, and the club would like to get a response — even in the form of a counter offer — by the weekend, the sources said.

That is about an average of 6.75 million over the length of the contract. Many think Letang could get up to eight-million a year if not more on the open market.

Some comparable contracts from the NHL best defenseman

So this contract would make Letang the 7th highest paid defensman in the NHL. And, that honestly is what he is worth at this point. He isn't top five, but he is close. 
It is a fair deal, but Letang could be too into himself and reject it.