This conceptual paper proposes a model of adult L2 pronunciation development that integrates explicit segmental and suprasegmental instruction, literacy training with the International Phonetic Alphabet (IPA), and technology-mediated practice. Building on empirical findings from pronunciation pedagogy, this model outlines a five-stage pathway by which explicit pronunciation instruction improves adult learners' listening and speaking proficiency via IPA literacy development and artificial intelligence (AI)-based practice that can result in improving learners' real-world communication. While suprasegmental features have often been prioritized in the literature, recent evidence highlights the complementary role of segmental accuracy in achieving intelligibility. The proposed model emphasizes the importance of explicit, symbol-based instruction for adult learners, who can benefit from metalinguistic awareness and autonomous practice. Although theoretical, the framework offers a foundation for future empirical research and practical curriculum design, particularly in English as a foreign language (EFL) contexts, where pronunciation instruction remains underdeveloped.