There's a lot of things that need to change before we consider lifting the limit, and those who think that lifting the limit will magically solve these issues are usually biased Fenerbahce fans.
First and foremost, look at the current line-up of foreigners in the league, these are the players that were signed with less freedom because the club's are under more pressure to make the right decisions when they have a limit to stay within.
Here's the list, minus Fenerbahce, Galatasaray and Besiktas. It's scary stuff, so you might want to go take a piss and prepare yourself:
Ankaragucu: Andres Lamas, Andre Silva, Bebbe, Kirita, Paulauskas, Kaba Diawara, Augustine, Jiri Masek, Ibrahim Said, Jaba
Ankaraspor: Fredrik Risp, Tita, de Nigris, Hamilton, Senecky, Neca
Bursaspor: Vandelannoite, Mbesuma, Renny Vicente Vega, Romaschenko, Ronald Gutierrez, Ysrael Zúñiga, Herve Tum
Caykur Rizespor: David González Giraldo, Anderson, Nascimento Ribeiro, Gustavo Victoria, Igor Gal, Leandro Chavez Rodrigues, Dennis de Crues, Carlos Rodriguez
Denizlispor: Carlos Alberto, Tomas Abraham, Julio Cesar, Roman Kratochvil, Souleymanou Hamidou, Karel Kroupa
Gaziantepspor: Zurita, Afanou, Deumi, Neira, Ivan, Sedlak, Beto, Matumona
Genclerbirligi OFTAS: Jevtic, Tozo, Petkovic, Sandro, Boadu, Yakubu
Genclerbirligi: Traore, Kahe, El Saka, Isaac Promise, Adamu Mohammed, Nicolas Peric, Daniel Addo
Konyaspor: Washington, Kaue, Ze Gomes, Damir Kahriman, Tehoue, Mihajlov, Cedric Sabin
Kayserispor: Juan Pablo, Iglesias, Toledo, Cangele, Saidou, Ivankov
Kasimpasa: Andre Moritz, Ely Cisse, Desire Yousef, Khalid Sinouh, Fransergio, Jens Berthel Askou, Edin Ademovic
Istanbul B.B. : Hasagic, Tjikuzu, Adriano, Marcus Viniscus
Manisaspor: Borbiconi, Rafael, Kalabane, Dalgaard, Allyson, Martinez (GK), Tiago Targino
Sivasspor: Diallo, Sylla, Okorowanta, Cvetkov, Balili, Petkovic
Trabzonspor: Moawad, Jabi
So divide the quality on that list by about 2, and then double the number of names on it, and that's what you'll have as the line-up of foreigners in the unrestricted Turkcell Superlig.
If we can assure that good quality players, unlike most of that above list, are going to come into the league then I don't mind a lifting of the foreign limit. But there's no way to govern that, who can label a player of good quality and how?
You can't limit it to internationals only, because look at the list above, one of the good players on there is Cangele - an Argentine without a hope in hell of playing for them. Matias Delgado has very little chance of playing for Argentina, Aurelio had absolutely no hope of playing for Brazil, but these guys are all good foreigners in this league.
Another method is to prevent slave labour rates by restricting a minimum salary rate for foreigners, It protects them and forces clubs to think about their investment or go bankrupt for being overzealous on the transfer market. $200,000/yr translates to 10 foreigners costing at the very least $2m/yr, plus transfer fees. It's not a bad system but also has it's flaws too.
There's a lot more to consider than "the pool of talented foreigners is better than the pool of talented Turks, therefore it's a good idea". It's a short sighted and in the case of a Fenerli, greedy train of thought.