The hundreds of Sabbatean Rabbinic Jews who followed rabbi Sabbatai Zevi and accepted initiation into the Bektashi order never converted to Islam. They were nevertheless excommunicated by the poskim (rabbinic decisors) due to the Sabbateans risking to expose Bektashism and the other six denominations of core Median Judaism as constituting Judaism and thus also exposed the seven denominations (Alawism, Alevism, Alianism, Bektashism, Druzism, Yarsanism and Yezidism) to the risk of forcible conversion by political Islam.
The fact remains however that the Sabbateans did not become Muslims but rather became Bektashis and transitioned from the Southern Jurisdiction of Judah to the Northern Jurisdiction of Israel. Not only do Sabbateans remain Jewish but Sabbateans remain just as Jewish as other Bektashis. Sabbatean conversions fall under the religious authority of the Northern Jurisdiction of Israel, specifically the Bektashi order and are therefore just as valid as other Bektashi conversions.
However, specific conditions apply. Since the Sabbateans are now part of the Northern Jurisdiction of Israel will the top poskim not officially acknowledge the Sabbateans as Jewish in keeping the secrets of the seven denominations of core Median Judaism. The only question of course is for how long the nominal “secrecy” will remain in place now when the big secret of Median Judaism is out of the bag? The answer is that it is up to the Israeli government to choose the time for announcing to the Israeli people and the world that Median Judaism and Median Jewry do exist.
The good news for the Sabbateans is that their religious “excommunication” from the Jewish people will de facto end when the 27 centuries long separation between the Southern Jurisdiction of Judah and the Northern Jurisdiction of Israel ends and that is certainly on the horizon. Sabbatean Jews of course are fully Jewish and even now actually fully entitled to Aliyah (immigration to Israel) under Israel’s Law of Return.