Many people think that it is useless to pay now. Anyway, we will enter the pool. We have already said this for a long time. Recently, CIC has issued an official answer, which reveals the time and some basic principles of Express Entry. The full text is as follows:

Will skilled immigrants be considered under both the current admissions system and Express Entry in 2015?

No. Each application is assessed according to the eligibility requirements and caps in place at the time CIC receives it. In order to be considered for Express Entry, people will have to apply separately (starting in January 2015) using a new electronic application management system. There will not be any application caps or occupation lists under Express Entry.
There is always a time lag between when people apply and when they settle in Canada. As a result, there will be an overlap between people being processed under these caps in 2014 and people applying under Express Entry in 2015.