I am working on publishing my Robinson-Pierpont edition of the Gospel of John. I am adding a footnote in all editions regarding John 3:15, as follows:

εν αυτω                                                     εχη           𝔓⁷⁵ B Wsupp 083 0141 SBL TH NA28
εις αυτον                                                   εχη          ℵ 086
επ αυτω                                                     εχη          𝔓⁶⁶ L
[εν αυτω]                                                   εχη          𝔓³⁶
εν αυτω       μη απωληται       αλλ          εχη          T
επ αυτον     μη απολ___         αλλ          εχη          A*
επ αυτον      μη απολητε         αλλ          εχη          A²vid
εις αυτον     μη αποληται        αλλ          εχη          𝔓⁶³ G K N U Δ Θ Π 063 TR RP
εις αυτον     μη αποληται        αλλ          εχει         E F H S Y Λ Ψ Ω 047 0211
εις αυτον     μη αποληται        αλλ          ε__           V
εις αυτον     μη απωληται       αλλ          εχη          Γ
εις αυτον     μη απωληται       αλλ          εχει         M
lac           C D P X 070 0233

In order to say “believe in him,” John usually writes εις αυτον, so εν αυτω was probably original, and scribes unconsciously wrote the familiar εις αυτον.  Now, since εν αυτω is not usual for John for “believe in him,” it is possible that the text with εν αυτω means, “so that everyone who believes, may have eternal life in him.”