Again there was never a possibility of the South African teams joining either the English or French leagues, they are simply not looking to expand.
I'd say the chances of getting into the Champions Cup are much better than slim with the move into Pro Rugby, probably more likely than not within two to three years but its virtually zero if they don't join .
People who knock the standard of the Pro Rugby invariable don't actually watch it. A lot of the criticism comes from English rugby fans who love to knock the league particularly when teams from the Pro 14 beat English teams in Europe.
Yes there is an issue with the Irish teams fielding B sides for many games in the Pro League, but it doesn't really apply to the Welsh as much as they don't have the squad depth the Irish teams do and usually only two of their four teams gets into Europe and they usually don't make it out of groups. A big part of fielding weaker teams is also to do with the Six Nations affecting the Pro Rugby clubs worse than than England and France. England and France are calling up player dispersed among ten teams, with the Pro nations all the national call ups are coming from either four or two teams. That's not really the fault of the Pro Rugby, it just happens to clash with the Six Nations.
The only alternative is South African teams playing solely in an even shittier Currie Cup.
If the South African teams quality is as good as your implying here and they are allowed qualify for Europe from Pro Rugby qualification spots, then you will force the better teams to play their stronger sides more often or risk losing out on qualifying for Europe.
With the attitude you have, I'm sorta of under the impression you think the South African team's will just waltz Pro rugby. Guarantee you that the South African teams will struggle against the stronger teams of the league when playing away from home, even against the so called B sides of those teams. After all Super Rugby might have had the best standard of rugby in its prime but from my understanding South African teams have only won Super Rugby three time, not once in the last ten seasons and are far from what the would be considered the standard setters of Super Rugby. I don't think any South African team will come close to winning Pro Rugby it in the first couple of years.