I will check with the Product Manager for Collections but I have not heard of any plans to do this.
To open a PST to see whats inside requires that the PST needs to be copied to the Clearwell Appliance then opened using the Outlook api's copying the PST to the Clearwell Appliance is faster than trying to open it over the LAN or WAN.
The only way that would make sense to make this work is to have an agent that can leverage Outlook on the machine your collecting from to open the PST then from there search the content and extract the items that matches the search parameters. This would add a heavy load on the source PC and may become counter productive as well as taking much longer to search the content as a desktop will not have the capabilities and power as the Clearwell Appliance