It sounds a bit like an irony of fate: Requisite for the upcoming WordPress 3.2 release are improvements in resource usage and maintainability: Speed, Performance, less memory, better tested (WordPress 3.2, the plan: faster, lighter). And this truly is of need.
But it will be the first release since years that will actually allow you to finally raise the memory limit over the hard-encoded 256 MB limit. Current stable releases neglect a higher setting within your php.ini file and downgraded any value to 256 megabyte.
So we will be able to use more memory with WordPress 3.2 then.
That’s good news. I had hoped this would have gone already into 3.1 already but well, it’s good to see that this ticket could be resolved within less then 12 month finally.
Just some days ago a patch went in that allows to configure the maximum wordpress memory limit. It will become available in the 3.2 stable version.
Configure the WordPress Maximum Memory Limit (Admin, Images, Zips)
Next to the existing WP_MEMORY_LIMIT constant, users will be able to additionally either configure their blog using a constant called WP_MAX_MEMORY_LIMIT and plugin authors can make use of two hooks admin_memory_limit and image_memory_limit. Previous hooks did not consequentially deal with all parts of the software to reflect a filtered value properly.
The recommended practice is to set your memory limit in the M shorthand notation (e.g. "1024M" for 1 GB) for WordPress within your PHP configuration and within these configuration values/hooks to prevent running into a related issue (#14889, Technical Installation Checklist).