This chapter tests the hypothesis that a shift from an L1 to a community-dominant language as speakers’ main public language is abrupt, not gradual (i.e., from one grammatical system to another, without implying L1 grammatical attrition). When the situation biased urban Xhosa-English bilinguals in South Africa to speak only Xhosa, many speakers showed Xhosa-English codeswitching (English content words in Xhosa grammatical frames). Such codeswitching does not necessarily predict a shift. Rather, in such a situation the frequency of L2 monolingual clauses (English here) does point to a shift and its abruptness. A cluster analysis divided the sample (N = 48) into three groups based on use of English elements; the ‘front runners’ group showed numerous English clauses.