If we extended his contract significantly that to me would indicate we are pushing up his market value.

As we have not done that only added a year, in my opinion this indicates he will be here to stay.

Very pleased with this news but the test will come if we do get a bid from the NRL. I hope he is contented and has made the decision his future is here but I am not confident if enough money was put on the table IL could resist it regardless of who we had to replace him.

The last part is the most important. At present we don't have anyone to replace him. I have high hopes for Luke Waterworth, but he is only 17 years of age, so you are looking at four years minimum before he will be ready (if at all) The Charnley situation is a bit different in that Manfredi is much closer to being ready for first team level, and we have Gelling/Thornley who could play there.

I get really worried now whenever one of our players signs an extended contract.

From what i've seen of them both - Gelling and Thornley are not the answer. We could sell them both and put their combined wages towards someone decent...

Maybe IL has changed his mind.
Perhaps after witnessing all the departures he and SW had decided that we have to put an end to the exodus.
MM has come along and said he's had interest from the NRL and perhaps IL/SW have told him he's got a three year deal and he's going nowhere. They then, to keep him happy, offer him an extended deal with a hefty pay rise, knowing full well there isn't an alternative player at the club. MM accepts and everyone is happy.
If there is another player perhaps he's been told the same, you have an x years contract and you're going nowhere. Because of the way his agent handled matters no doubt they would follow up with advice that he's paid very well and no pay rise is coming his way.
One player is very happy, the other will realise he has to live with it and it's in his best interests to forget about a move and become better at the job he already has and for which he's paid well.
I do think this could be the policy change from the club we've been wanting on here since the end of last season and long before that too.
If it is I'm very happy about it.

Also could it be especially in Charnley's case his agent tries to be clever knowing about the 100k of his wages going on the cap tries it on and makes noises about NRL and union. But the club calls his bluff knowing that Josh is buggered if the club plays hardball with players who will get the development exemption.

I do sometimes think that agents will start a rumor to get a wage hike. If the club starts to make players honor their contracts we can look forward to stability. But i do not hold my breath.