I can only give you my personal opinion, but I would not spend money on either option frankly. The 350 setup is easily the worst thing out there from Pioneer (imho), loading times on anything but the smallest of collections on a RekordBox-stick is pretty bad, the display very limited, searching – already a b*tch on any one-knob system – seems even worse on the 350s.
As a CDJ-alternative the XDJ700s are clearly a few classes better than the 350s, but at the end of the day they are still just CDJs but without CDs. If you want the extra functionality/creativity offered by DJ software, then it does not make much sense using an external mixer. Even with USB connectivity you would be missing a LOT of functions that a controller would offer you by way of extra buttons, knobs and even faders.
As far as new coming gear is concerned, usually you won’t know til very shortly before things are officially launched. Imho it’s really bad policy to postpone the purchase of new gear because of thing that might be coming next.
My recommendation would be to read some of the recent posts on the topic of picking your first controller. There is a logical multi-step approach to determining what gear would fit you best, starting with determining your workflow. From there it get’s easier to narrow down your options. Worfklow, software (if you are going that route) and budget together will lead you to a shortlist of gear. The two setups you mention for example would, again in my opinion, never fit in the same shortlist as they are far apart in features and price.
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