Depends on which add-ons you currently need. Just because XF 2.0 is out does NOT mean that it fits everyones needs. There are many add-ons that are not currently compatible with 2.0.
Two major ones as an example or Bob's Showcase and Articles systems. If your site needs them then XF 2.0 is out of the running currently.
XF 1.x will not be "phased out" soon. It will be supported for a while yet as XF developers would be shooting themselves in the foot if they quit supporting it before more add-ons (the major ones) were updated to work with XF 2.0.