Did you read the first line of that post? "What happens if both leave AND we trade away Sgarbossa?" As in a question of what you think should happen in that scenario of Downie and Stastny not re-signing with the team. My explaination was setting up the possibility, which has some high probability that we don't re-sign Stastny and Downie. Stastny might look for a guaranteed top 6 center role and Downie might want too much money for his role. Both are fairly likely to happen. So, if we are going to trade away depth you have to be sure that you can survive without those players coming back or have a very good idea that you will re-sign those players.
I would say the odds of not overpaying for a UFA are pretty low. How many bargain UFA contracts are out there... PAP, Hossa (manipulated contract)... that is about it. While 2nd/3rd liners like Clarkson and Clowe signed for 5.25 and 4.85 per in this year's free agency period.
I guess here's more or less the way I view that line of thought in relation to what we're talking about.
Like I mentioned that line of thought involves a lot of worst case scenarios, or bad scenarios. You're right Stastny and Downie could both easily leave, and they might not get a return for Staz at the deadline. The chances at getting a great value contract like PAP every UFA period is pretty low. Hishon and the entire Avs forward prospect pool might not pan out. Sgarbossa might turn into a very good 2nd line winger. Klesla could walk at the end of the year, miss more than his usual 15-20 games, or just demand too much money. Tanguay may turn into David Jones in a year or so. They may go 2-3 yeas without being able to find a fair deal ($4M or under) for a decent 2nd line winger. They may not be able to find a decent trade in that same 2-3 years for a 2nd line winger.
All of these things have a chance at happening, and some like you say might have a better chance at happening than not.
However it's not about just one of those things happening, making the whole trade a bad one. The way I view it, in order for them to get burnt somehow, or regret moving Sgarbossa ALL of them have to happen, and the odds of that are very slim IMO. That's basically been my whole point in this discussion, and why I tried to point out all their options.
Also the spot you're worried about having to fill in the future is generally one of lesser importance being a 2nd or 3rd line winger. This is generally one of the easier spots to fill in a lineup. The Avs also have very good depth at forward, and are set up very well cap wise with Duchene and Landy's deal for the future. Even if they add an over paid winger like many contending teams do, they are set up to be able to absorb that.
As I mentioned all of those things above have to happen for them to get burnt losing Sgarbossa, and if they can make one of the scenario's work (i.e. Hishon, Tanguay's play doesn't slip, they find a reasonable $3-4M winger that they can afford via UFA, find another forward in trade like they have a history of doing, Klesla re-signs and plays a solid role for the next 3 years taking over for Hejda, then it's worth it IMO.
I feel pretty confident that they will be ok under at least one of these scenarios, and worst comes to worst, under the very unlikely situations that NONE of the scenarios pan out, they still have a very good group of young forwards so the actual damage done is not that strong to begin with.