What will happen if I attach the suffixes "-ize" and "-ify" to a word that end in /ŋ/? Will they make it [ŋg]?

Solution 1:

It could be pronounced either way. Compare diphthongise (-ize) which is derived from diphthong (ends in /ŋ/) and -ise and is mostly pronounced with [ŋ] (I've heard it pronounced [ˈdifθɒŋɡaɪz]). For diphthongise, Lexico and Merriam-Webster give the pronunciation with [ŋ] only:

• /ˈdɪfθɒŋʌɪz/

However, Collins Dictionary and Dictionary.com list the pronunciation with [ŋɡ] as an alternative.

As for the suffix -ify, I think it can also be pronounced in both ways; with [ŋ] or [ŋɡ]. There aren't many ify-verbs that have [ŋ] before the -ify, the only one I've been able to find is stringify for which Wikitionary gives /ˈstɹɪŋɪfaɪ/ only.