Migrate from crm 2011 to crm 2013

Hello,

I migrated crm 2011 from crm 4.0. Plug-ins from crm 4.0 are working on crm 2011 well. I read that sdk of crm 4.0 is unsupported on crm 2013. Do i need to registered plug-ins rewrited for crm 2013 in crm 2011 before upgrade?

or i can upgrade crm 2013 from crm 2011 and update plug-ins later (which are writing with sdk of crm 4.0)?

Thanks

Regards