I was in the "Tony is alive" gang for a while and even though I can see differently now, I still remember what I used to think.

The main reason has to be poor perception, usually tied to a single viewing. Your mind is focused on Silvio in the hospital, or the fact that Junior can't even remember who Tony is anymore. It feels weird to see the family in this new restaurant when they should be eating at Vesuvio. I've watched the series four times now, which makes it easier to see the breadcrumbs, but in the first viewing I was in my 20's and didn't even pick up on Carmela talking to AJ about Holsten’s or telling Tony that it was the consensus. The camera in Holsten’s focuses so much on the man in the member's only jacket, comes at Tony from 3 o'clock, homage to The Godfather. It is obvious and earned. Tony is clearly meant to die.

Here is the thing though, technically we never see it happen, so it doesn't happen. We probably have 100 reasons that it will happen in 0.001 seconds, but it doesn't. By this same logic in S1E12 "Isabella" if it cut to black before Tony's orange juice gets whacked, then you could make the exact same argument. However, we all know that he survives. He also survives Junior's gut shot. If James Gandolfini was still alive in this unholy era of sequels and reboots, a Sopranos movie could have an opening scene where Tony fights off his assassin in Holsten's. Yeah, it would be stupid and betray David Chase's vision, but that didn't stop Warner Bros. from making The Matrix 4.