I'm in the same boat, bought my Traffic from new in 2015 with the aim of replacing it after 10 years. Paid 14k plus vat for a top spec van and now they have tripled in price. Crazy.
So I've decided, like others have said to carry on with my old van till it dies. I've looked after it, serviced it to the letter, never thrashed it. About to replace the timing time soon as a precaution. So no reason it can't carry on.
Okay, if I need to replace something big like a gear box or turbo it will be a fraction of the cost of new van.
I reckon in 5 years time things may be different with much better and cheaper electric options.