Short answer: no! Let us take a quick look at what makes it 1) "poor" and 2) "sexy".
1) Berlin is considered "poor" because on the one hand a significant % of population is made up of persons who have smallish or no earned income, and on the other hand has few individuals earning top money. The first group is made up primarily of young people who feel just fine as they are--they are not like impoverished/unemployed older persons with dependent. The second group--which is "abnormaly" small, is usually found among top executives in large financial or industrial companies, which in Germany are headquartered in Frankfurt, Munich, Duesseldorf, Stuttgart and Hamburg, but not in Berlin anymore since the end of WW2. (Berlin had been the largest industrial city in Europe). Furthermore, while the city has regained its title of Capital City, note that it is a federal state, not centralized like France, and on top of that virtually 50% of federal ministries/agencies are located elsewhere (Bonn etc.) So the net effect of the capital transfer has been minimal (also taking into account the loss of the capital function of the former GDR in the east). Finally, bear in mind that when the former mayor coined that term ("Poor but...) he must have had in mind a kind of tactics to attract sympathy, and thus money... from the rest of the country.
2) "Sexy" because of all the young peoples who were attracted to a place which combined low rents AND a vigourous art scene, combined with 1) generous state subsidies, 2) housing in central areas (of former East Berlin) with a great potential for "experiments", etc: once the movement was set, it had acquired a momentum of its own, now attracting more "yuppie" types.
THUS (very briefly) Conditions are in place for further development in the arts, tourism, and to some extent scientific research, but there will be no serious return of big business. At the same time, the more marginal components-- often deemed "poor" of the population might (with some resistance) move away from the centre towards more welcoming (for them) settings in the March of Brandenburg...