Pending upgrade. Is it free?
One of my linodes says, "You have a pending upgrade. The estimated time to complete this upgrade is …"
Does this mean that I (or someone else on the account) requested an upgrade? Or is the current VM a discontinued product? Or something else?
Will this upgrade change how much the linode costs per month?
I'm not sure what the circumstances of your "upgrade" are but I've received several of these during my tenure as a Linode customer. They have always been free.
Linode offers these periodically to cement customer loyalty or when their operating costs drop significantly enough to allow your subscription fee to buy more. Sometimes, it's migration to a newer, faster physical machine and other times it's a bump in disc space or memory for your plan.
I'd just accept the upgrade. Be forewarned that your Linode will be stopped while the upgrade is in progress. I believe that Linode allows you to schedule them for the middle of the night or whenever it's convenient for your Linode to be turned off for a few minutes.