Não testei
@Override public boolean onCommand(CommandSender sender, Command cmd, String arg2, String[] arg3) { Player p = (Player)sender;
if (cmd.getName().equalsIgnoreCase("teste")){ Bukkit.getScheduler().scheduleSyncDelayedTask(Main.main, new Runnable() { public void run() { p.openInventory(menu1); } }, 40L); } return false; }
Só trocar o openinventory por sendMessage