According to sources close to a motherboard manufacturer, Nehalem CPU in its 1366 socket won't get to mainstream by volume or price until Q4 2009. This might sound shocking to many, as you might expect to upgrade to a quad-core mainstream Nehalem in mid 2009; and unfortunately it won’t happen, at least not for a few hundred Euros / Dollars.
Nehalem will definitely launch as an ultra high-end desktop and server part in Q4 2008 and it will take time until this marchitecture sinks to the attractive $200 to $300 price range.
Therefore, don't worry about Intel's soon-to-be launched P45 boards and the LGA775 socket, as it will serve you well for some time to come. After all, P45 is a 65nm chipset, and hey, that is better than the 90nm P35, X38 and X48; at least it sounds like it.