Not yet.
Adobe's free upgrade policy, and the asssociated eligibility period, kicks in after a new product or upgrade is out of beta and has been announced. Details will be made clear on the Adobe website.
http://helpx.adobe.com/x-productkb/policy-pricing/upgrade-policy-produ ct-announcement.html
This policy does not apply to betas. You can use the LR5 beta through until June 2013 - then buy LR4 when the shipping version of LR5 is announced.
Announcement to shipping is anywhere from 2-4 weeks or longer.