I think it would be a large negative for NYC bond-holders and NYC pension holders.
Of course any random change could result in NYC dwindling away and not being able to pay it’s bond obligations any more. We don’t have to posit a radical change in how taxes are collected to imagine that, we just have to look at Detroit. The whole point of a bond is that when you purchase one you are betting that the city will still exist and still be able to pay the interest on the bond. That’s never guaranteed though.
And surely the pension holders would be fine, since those obligations will be funded from investments NYC has made whose performance is independent of its own revenue.
1. NYC funding sources will remain as they are today, or
2. NYC will transition entirely by 2038 to a land value tax?
To the extent and for the entirely rational reasons that you prefer #1, that's the negative to NYC bondholders.
> surely the pension holders would be fine, since those obligations will be funded from investments NYC has made
Assuming the pension was funded to 100% of projected obligations, this would be true. That is not the case; it's around 4/5ths funded.
Likewise pensions. My personal opinion is that anyone accepting a pension instead of better pay is not really doing themselves a favor; they’re taking on extra risk that the politicians won’t raid the pension fund or otherwise mismanage the city. I would rather just own the underlying securities myself, and eliminate the extra steps.
If you disagree, that's OK, but there's probably no way to make further progress in resolving that disagreement beyond a back-and-forth of "nuh-uh, yuh-huh".
Now all of those people are working remotely, living wherever they want to live, and are no longer forced to live in Manhattan. They no longer have to commute, so they're not adding traffic at all. They still need services, but they’re paying property taxes in whatever place they live in, so those are still paid for. In fact, the “headquarters” is really just the CEO’s house, because now _everyone_ is working remotely.
JP Morgan still needs bank branches all over the place, and some of those are in Manhattan. JP Morgan must pay the land–value tax for the land that those branches occupy, and that money pays for the city services required by the branches. They’ll still have the same number of branches before and after the move, so that won’t change.
JP Morgan still needs datacenters. The largest ones will be located where the land value is the lowest, of course. However, it will still be necessary to interconnect with multiple backbones, and the best place to do that is in the city where many companies are very close to each other. That won't change either.
I don't see how this would be a negative for anybody. People who want to live in a dense city still can. Businesses who want to operate in a dense city with lots of nearby customers will still do so, even if the land value taxes are higher; the revenue will be higher as well so it will be worth it.