I'll explain this further:

The Linux kernel supports enormous amounts of hardware devices (e.g mass storage, usb devices) and CPU architectures (e.g. x86, ARM). The installation of the kernel and it's modules can be as small or as large as you want them to be.

For example I used to have a custom install of Slackware(current) on my laptop. It includes kernel version 2.6.33. Great kernel but the wireless driver breaks on my hardware. I replaced the kernel with an older version - 2.29.6 worked perfectly. The rest of the software still runs fine with the older kernel. I did not need to re-compile anything. E.g. Firefox, Openoffice and cd/dvd burning was fine.

I also installed all this on another laptop (much older)- but could use the latest kernel (2.6.33) and everything was still ok (the older kernel worked too). Both laptops were x86-based but were completely different specifications.

This older laptop could not use compiz special effects so I had to switch them off but the installed applications still ran fine.

I see no reason why MeeGo can do the same thing with older Nokia devices. If we talk about hardware abstraction then different kernel configurations would be needed but the higher-level stuff like user applications should stay the same.

Imagine if MeeGo was available for the n900 and n800.
The n900 is capable of making phone calls the n800 cannot do that. The only difference should be the driver. The rest of the software should still be the same.

However if we consider the n770, n8x00 & n900 in the same "family" then MeeGo can unify these devices together. Just because a device is older does not always mean "less-capable". Pre-n900 devices support OTG usb and use larger screens.

I know that mobile devices vary wildly compared to PC-type systems but I think many of the principles are the same.

As long as Nokia, Intel and other companies adhere to the MeeGo "standards" then cross-platform and older devices can benefit from this.