I tend to agree, and always use the wifi option on my Nokia N95 8GB where I can in preference to the 3.5G mobile broadband for just that financial reasoning. Plus wifi tends to be more reliable/stable.

Given the massive cost difference between wireless hotspots and mobile broadband (not to mention the difference in bandwidth, up to 54MBit for 802.11 vs. 1.8MBit for wireless broadband) it's unlikely.

Wireless broadband through my ISP would cost me €80 per month with a bandwidth limit of 2GB.
802.11 access through the hundreds of hotspots they provide nationwide (mostly in public buildings and public transportation nexi) is free and has no bandwidth limits.

Just about the only advantage of UMTS/GPRS is the availability. Instead of having to stay near that hotspot you can use it anywhere you're within reach of a cellphone tower and move around almost anywhere instead of loosing the network if you're outside the area of the WLAN.
For that reason my employer has supplied each employee with a UMTS card and account for emergencies. If we're somewhere with no internet access and we need to access the company intranet (say to fill out timecards or check email) we can use that, but due to the high cost we've been given a strict datalimit of 500MB per month (which is I think cumulative, rather than being lost when not used, but that's details).

At the same time we have a company wide WLAN set up for everyday use at considerable cost (multiple high capacity hotspots on each floor to cover for the maybe 500-1000 people who connect to it every day).

So no, WLAN is going nowhere for the time being. UMTS will gain ground as the price drops, but it will remain a plaything for most people and a sometime tool for those who require access to their company networks (and maybe the internet) at inopportune moments when they have no other means to get it.