The current Tamagotchis in Japan are the Tamagotchi Plus Series. As you can see from the BANDAI Co., Ltd. Press Releases (in English), they are currently up to version 3 in Japan.
https://www.bandai.co.jp/e/releases/index.html
The article 2006/04/12 "Tamagotchi Plus Series Worldwide sales break the 20 million unit" mentions the following:
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The following 3 products have been released so far in the "Tamagotchi Plus Series":
Version 1 Launched Mar. 2004 Kaettekita! Tamagotchi Plus (¥2,079)
Version 2 Launched Nov. 2004 Shuku Ke-tai Kaitsu! Tamagotchi Plus (¥2,625)
Version 3 Launched Nov. 2005 Cho Jinsei Enjoy! Tamagotchi Plus (¥2,940)
Connect and enjoy playing with other Tamagotchi through the infrared communication function. Version 2 can be linked to a mobile phone, and Version 3 to a computer website or a mobile phone.
* Tamagotchi Plus Series planning and product development is performed jointly by BANDAI CO., LTD. and WiZ CO., LTD.
* Prices include tax. Currently only "Cho Jinsei Enjoy! Tamagotchi Plus" is available in Japan.
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The current Tamagotchis sold outside of Japan are the Connection or Connexion. Again, as you can see from Bandai America Incorporated's News Releases, they are currently up to version 3.
https://www.bandai.com/news/news_index.cfm
The article March 29, 2006 "Bandai America's Tamagotchi® Connection® Continues to be the Hottest Selling "Virtual Pet" Around" mentions Tamagotchi Connection, Tamagotchi Connection Version 2, and Tamagotchi Connection Version 3 only.
If there were a real Bandai Tamagotchi version 4 (or 5, 6, 7, 8, 9, ...) product, there would be a Bandai news release announcing it.