There never was a 7.60.
Or rather, there was a planned 7.60, but it never happened. The press release for the Opera 8.0 beta explains why:
"We were preparing for the 7.60 release, but as work progressed and we kept adding improvements and functionality, it became very evident that we now have a browser that is so powerful, secure, and easy to use that it exceeds the next logical version number and warrants a major release"
We did release previews that had the version number 7.60, but previews are just that – previews, test versions, pre-alpha or alpha software which does not represent the next final version. Those who have followed us through a few preview versions will understand what I am talking about, as previews have been known to be very experimental in nature, introducing new ways of doing things specifically to get feedback on those things. That these experiments are available in previews does not mean that the next final version will look like that.
Opera 7.60 was originally supposed to be Opera 7.5 plus voice, and maybe some other small improvements. As time progressed, we found ourselves having to deal with other issues, such as Gmail compatibility, and soon the plans changed. Previews were released, and the version number was still set to 7.60, but towards the end of the preview cycle, what was left was not just 7.5 plus voice…
- We had a completely new version of the core in place, with improved support for various standards, as well as XMLHttpRequest support, needed for Gmail.
- We added a new rendering architecture, called ERA (Extensible Rendering Architecture), which lets you use Opera on any screen size, and Opera will reformat the page to fit.
- Printing received a facelift too, and fit to paper size was added.
- Opera 8.0 automatically checks for new versions every week.
- Error dialogs were replaced by error pages.
- Help files were moved online.
- We dropped the Java bundle, and instead offer to download the Java environment when you visit a page using Java.
- The user interface, including toolbars and menus, was streamlined and made more friendly to new users, and mail, chat and newsfeeds no longer have to be disabled. They are only enabled when needed.
If you read the changelog, you will understand why this is a new major version, and not just a minor upgrade. There are major changes to large parts of Opera, both visible and invisible ones. The e-mail client has not been prioritized this time around, as it got a major upgrade in 7.5, but there will be another major upgrade to the e-mail client in the (hopefully) near future.
To sum up, Opera 8, or whatever the final name will be, is not an upgrade to Opera 7.60, because 7.60 was never officially released. It is an upgrade to Opera 7.54, and the changelog since 7.54 should speak for itself.
And yes, people who bought Opera 7 will get the upgrade to the next version for free.
Opera 8 is a free upgrade.