Talking about new projects in Barcelona is like talking about what the weather will be like in a few years.
After the experience we've gone through around the construction of line 2 which was finally opened last year, noone in Barcelona would dare to foresee anything related to the planning and building of new lines or line extensions.
As you might have read on the HISTORY page, Line 2 was projected in the 50's and should have run from the city centre via "Sagrada Família" to "Horta". The first part of this line, from "Sagrera" to "Horta" was opened in 1959, but 11 years later this section was connected to the newly built line 5. Ever since then the construction of line 2 has been a story of speculation: a tunnel between "Sagrada Família" and "Sant Antoni" was excavated in the 70's but never finished. When Barcelona was chosen to host the 1992 Olympic Games, suddenly everyone remembered the dead tunnels underneath the city centre. Everyone seemed to agree that the line should be finished and bring visitors up the Montjuïc mountain where the Olympic Stadium is. But decision making took so long that years before the Games the engineers told the authorities that it was impossible to reach the stadium by 1992. They still decided to push the line forward and to open the first section, from "Sagrada Família" to "Sant Antoni", in 1992, but it finally took three years longer until this part was opened in September 1995. And after the Games were over, discussions started again and finally it was decided to renounce the Montjuïc part and use an already built station at "Paral·lel" as the definitive terminus. Now people in the district of Sant Martí, where 5 new stations of this line are being built, insist in concluding works on time, because they fear the same might happen again. At "Sant Pau" line 2 actually should take over the Badalona branch ("Pep Ventura") of line 4, but who knows what will be in the future...
-- Line 4 could be extended one or two stations from "Roquetes" to serve the neighborhoods of "Trinitat Nova" and "Ciutat Meridiana".
-- Line 5 should reach Line 3 in the disctrict of Horta, at "Montbau".
-- Line 3 might give up the terminus at "Montbau" and run further to the densely populated area of "Canyelles" and maybe connect to Line 4 at "Roquetes".
-- Sometimes plans have appeared in the press to build a light rail line or tram along Diagonal Avenue across the city. A first section might be started from L3 terminus "Zona Universitària" outbound to improve connections to suburbs like Esplugues, Sant Joan Despí or Cornellà.
-- In the next years a new railway station will be built for the AVE (Spanish high speed train) at Sagrera, about 500m from the Metro station with the same name. There is the idea to build a metro-like shuttle train which might be integrated into a future (circle?) line.